diff --git a/.github/workflows/amalgamate-ubuntu20.yml b/.github/workflows/amalgamate-ubuntu20.yml
index 14b8902..0611e84 100644
--- a/.github/workflows/amalgamate-ubuntu20.yml
+++ b/.github/workflows/amalgamate-ubuntu20.yml
@@ -1,18 +1,10 @@
-name: Amalgamate Ubuntu 20.04 CI (GCC 9, 8)
+name: Amalgamate Ubuntu 20.04 CI (GCC 9)
 
 on: [push, pull_request]
 
 jobs:
   ubuntu-build:
     runs-on: ubuntu-20.04
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          # Legacy/x86 compilers cause CI failures.
-          #- {cxx: -DCMAKE_CXX_COMPILER=g++-8, arch:                         }
-          - {cxx:                           , arch:                         } # default=gcc9
-          #- {cxx:                           , arch: -DCMAKE_CXX_FLAGS="-m32"} # default=gcc9
     steps:
       - uses: actions/checkout@v3
       - name: Compile with amalgamation
diff --git a/.github/workflows/ubuntu18.yml b/.github/workflows/ubuntu18.yml
index 63a1455..791582d 100644
--- a/.github/workflows/ubuntu18.yml
+++ b/.github/workflows/ubuntu18.yml
@@ -1,19 +1,10 @@
-name: Ubuntu 18.04 CI (GCC 7, 6, 5)
+name: Ubuntu 18.04 CI (GCC 7)
 
 on: [push, pull_request]
 
 jobs:
   ubuntu-build:
     runs-on: ubuntu-18.04
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          # Legacy/x86 compilers cause CI failures.
-          #- {cxx: -DCMAKE_CXX_COMPILER=g++-5, arch:                         }
-          #- {cxx: -DCMAKE_CXX_COMPILER=g++-6, arch:                         }
-          - {cxx:                           , arch:                         } # default=gcc7
-          #- {cxx:                           , arch: -DCMAKE_CXX_FLAGS="-m32"} # default=gcc7
     steps:
       - uses: actions/checkout@v3
       - name: Setup cmake
diff --git a/.github/workflows/ubuntu20-fastmath.yml b/.github/workflows/ubuntu20-fastmath.yml
index eda488a..90f5347 100644
--- a/.github/workflows/ubuntu20-fastmath.yml
+++ b/.github/workflows/ubuntu20-fastmath.yml
@@ -5,8 +5,6 @@ on: [push, pull_request]
 jobs:
   ubuntu-build:
     runs-on: ubuntu-20.04
-    strategy:
-      fail-fast: false
     steps:
       - uses: actions/checkout@v3
       - name: Use cmake
diff --git a/.github/workflows/ubuntu20.yml b/.github/workflows/ubuntu20.yml
index 2704c85..2bbd973 100644
--- a/.github/workflows/ubuntu20.yml
+++ b/.github/workflows/ubuntu20.yml
@@ -4,15 +4,7 @@ on: [push, pull_request]
 
 jobs:
   ubuntu-build:
-    runs-on: ubuntu-20.04
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          # Legacy/x86 compilers cause CI failures.
-          #- {cxx: -DCMAKE_CXX_COMPILER=g++-8, arch:                         }
-          - {cxx:                           , arch:                         } # default=gcc9
-          #- {cxx:                           , arch: -DCMAKE_CXX_FLAGS="-m32"} # default=gcc9
+    runs-on: ubuntu-20.04                      , arch: -DCMAKE_CXX_FLAGS="-m32"} # default=gcc9
     steps:
       - uses: actions/checkout@v3
       - name: Use cmake